Some geological factors affecting the Upper Freeport coal and its quality / Edwin F. Koppe.

PROGRESS REPORT 159

Pennsylvan i Geological Survey

Fourth Series

SOME GEOLOGICAL FACTORS AFFECTING THE UPPER
FREEPORT COAL AND ITS QUALITY

By

Edwin F. Koppc

COMMONWEALTH OF PENNSYLVANIA
DEPARTMENT OF INTERNAL AFFAIRS

Genevieve Blatt, Secretary

TOPOGRAPHIC AND GEOLOGIC SURVEY

Carlyle Gray, State Geologist

1961

21 m\

PENNSYLVANIA S ATE LIBRARY

SOME GEOLOGICAL FACTORS AFFECTING
THE UPPER FREEPORT COAL AND ITS QUALITY.

ABSTRACT:

The Upper Freeport coal in the Freeport and New Kensington quadrangles,
Pennsylvania, varies from a bony streak to a thick coal deposit often exceed-
ing ninety inches, the “Double” or “Thick Freeport”. Distinctive basal part-
ings, a central bone layer, and a canneloid top bench may be present.

The appearance of a sandstone roof, sandstone rolls, and bony coal at the top
of the main coal bench can be anticipated in thin Freeport areas when basal
partings are absent. When the two basal partings are present, a shale roof is
normal. These effects are correlated with the original topography upon which
the coal was deposited. The original depositional high areas tend to coin-
cide with present structural highs.

Preliminary data indicate that coal quality, in part, is affected by the deposi-
tional setting. In “high” areas, a tendency exists for the main coal bench to
contain higher percentages of fusain and mineral matter. Within limits, some-
what higher ash fusion temperatures appear to correlate with paleotopographic
highs.

/4s a result of these findings, critical examination of the paleotopography and
related sediments is indicated in other areas and other coals.

Edwin F. Koppe

The Upper Freeport coal is quite variable both in
thickness and composition in the Freeport and New
Kensington quadrangles of Pennsylvania (Figure 1).
The coal horizon in these quadrangles is marked
either by a thin carbonaceous shale bed or by a single
bed containing a variable number of partings (binders).
The complex coal zone known locally as the “Double”
or “Thick Freeport” contains the Upper Freeport
Coal Bed at the base; but in addition, it has an over-
lying bone layer and an upper coal bed occasionally
capped with a canneloid layer. The “Thick Freeport”
often exceeds 90 inches in thickness, whereas the

E. F . KOPPE is Coal Petrologist, Pennsylvania
Geological Survey, Dept, of Internal Affairs, Harris-
burg, Pa. TP 59F312. Manuscript, Oct. 9, 1959. AIME
Trans., Vol. 217, 1960. Coal-IndM D Meeting, Bedford
Springs, Pa., September 1959. This paper is publish-
ed with permission of the State Geologist.

FIG. 1 Location of quadrangles.

coal usually varies

normal Upper Freeport
34 and 50 inches.

between

SCALE

Reprinted from AIME Transactions (Mining), 1960, volumi 217

185

FIG. 2 Structure contours, Upper Freeport coal. New Kensington and Freeport quadrangles.

Shaded portion is thick Freeport area. A — Wildwood column; B — Springdale column;
C — Armstrong column; and * — data localities.

To determine the causes of variation, a prelimin-
ary study was made of the basal partings in the coal
(Koppe, 1958). A characteristic distribution pattern
was found to exist throughout the Freeport quadrangle
which the author interpreted as a function of the de-
positional setting. Three related conclusions were
drawn for the area. They are: 1) coals lacking per-
sistent basal partings indicate topographically high
areas at the time of peat accumulation; 2) the appear-
ance of single basal partings suggests margins of
depositional highs or equivalent elevations; and 3)
two or more partings in the lower part of the bed are
indicative of low areas of earliest peat accumulation.
An extension of the studies into the “Thick Freeport”
area was warranted to determine relations where the
appearance of the coal is altered markedly by the
addition of coal above the normal body (Rayburn, 1924).

Figure 2 is a structure contour map of the area
under consideration. Present coal elevations were
used to establish the structure in the two quadrangles
(Hughes, 1933; Richardson, 1932). Structural features
from northwest to southeast are: the Bradys Bend
svncline, the Kellers'burg anticline, the McMurray
syncline, the Amity anticline, the shallow Freeport
syncline as a limb of the majo- Duquesne-Fairmont

syncline and separated from it by the local Leechburg
anticline, and the Murrysville-Roaring Run anticline.

All of the above structures plunge to the southwest:
however, mild interruptions of the trend are located
along the axes of the Kellersburg anticline, the
McMurray syncline, and the Amity anticline in the
southern portion of the New Kensington quadrangle.
These interruptions are found in the area of the “Thick”
Freeport” coal (Figure 2). Rayburn (1924) best describ-
ed the “Thick Freeport” coal area overall as having
“ — no well-defined anticlines or synclines and might
well be described as lumpy, but with no excessively
steep grades”. Locations of data from published lit-
erature (Hughes, 1933; Richardson, 1932; Ashley et
al, 1925; U. S. Bureau of Mines, 1939), mine records
and field observations used in the course of this study
are plotted as dots in Figure 2. In addition, some com-
pany information was examined which is not available
for publication at this time.

The parting distribution map prepared from the
above-mentioned data, reproduced as Figure 3, illus-
trates the regional changes in numbers of basal part-
ings. In the previous report (Koppe, 1958) the writer
postulated that the persistent partings in this area
mark depositional events which took place at two

186

separate times during development of the peat “blan-
ket”. Peat covered only lowlands when the earliest
parting was formed over it. The aerial extent of the
inorganic deposit therefore roughly corresponds to the
extent of peat accumulation at that time. After this
event, the organic deposit spread over topographi-
cally higher areas and the second inorganic layer
was deposited over the increased area of the swamp.
Peat formation resumed after this second event and
the swamp enlarged until all topographic relief was
submerged under the accumulating peat.

If the above interpretation is correct, it is then
possible to consider Figure 3 also as a map of the
paleotopography. The ancient topographic highs
(areas of no partings) occupy positions relative to
present anticlines suggesting that the paleotopography
was controlled by the same structures observable to-
day. The displacement of some paieotopographic highs
to the west of present highs well might be a function
of later deformation. In the southeastern quarter of
the New Kensington quadrangle, the axis of the Amity
anticline is indistinct. Here, the area of two partings
crosses the anticline connecting the two depositional
“lows” and a possible paieotopographic ridge cuts
across structure in a northwesterly direction. This
zone is marked by unexpected changes in the numbers
of basal partings and by the depression of present
structure, including reversals of dip. The zone roughly
coincides with the center of the “Thick Freeport”
area.

The relationships between partings and structure

are further illustrated in a northwest-southeast cross-
section of the Freeport quadrangle. The ralations
shown in Figure 4 may be of importance, especially
in coal mining. Structure along the line of the cross-
section is shown on the lowermost diagram in Figure
4. Coal profiles showing the relations of partings and
bone layers are illustrated in the centrally located
cross-section. The changes of cover sediments are
shown at the top of Figure 4. Near paieotopographic
high areas, shaly coal (or bone) is found at the top of
the bed. Non-persistent knife-edge shale and fusain
partings are abundant in the upper portion of the coal.
These are observed less frequently as the deposition-
al lows are approached. As shown in Figure 4, a shale
roof is normal in areas between depositional highs.
Massive Mahoning sandstone lies close to the coal
and produces more roily conditions and cut-outs on
and near the elevated areas. According to mine oper-
ators, sulfur content is generally objectionable when
sandstone contacts the coal. In general, the lower
part of the Mahoning sandstone grades laterally from
a massive sandstone on the original depositional
highs to an interbedded sandstone and sandy shale in
areas where a thicker shale unit forms the roof. The
vertical scale of the covering sediments has been
grossly exaggerated in Figure 4 to demonstrate these
changes. In the field, transitions are very gradual —
though sometimes interrupted by channel sandstones.

Sandstone rolls and cutouts are erratic in the
“Thick Freeport” area, although many are concen-
trated on local domes. One should recognize that

FIG. 3 Parting distribution of Upper Freeport coal.

187

erosion and subsequent sandstone deposition in the
“Thick Freeport” basin may have a later and differ-
ent mode of origin than the equivalent features in a
normal Upper Freeport area. Peat deposition contin-
ued in the restricted basin after cessation of peat
accumulation elsewhere in the study area.

Coal quality is affected to some extent by the
depositional environment. Excepting the local patch
of impure coal and coaly shale detected in the south-
eastern corner of the Freeport quadrangle, the normal
Upper Freeport coal tends to be uniform in quality.
Petrographic data of widely separated samples were
used in the preparation of Table 1 to illustrate this
point. Because the “Thick Freeport” consists of the
normal Upper Freeport coal plus a local overlying
coal, only the main bed can be compared with the coal
elsewhere. The Wildwood mine is located on the west
side of the “Thick Freeport” deposit; Springdale, on
the east side; and the Armstrong mine in “low coal”
fairly close to an old topographic high. These sites
are shown as sites A, B and C in Figure 2. The pro-
nounced differences are in the amount of fusain at
each locality. Thiessen and Sprunk (1935) reported
that the lower bench at Wildwood consisted of 57
percent anthraxylon, 39 percent translucent attritus,
three percent opaque attritus, and one percent fusain.
On the other side of the “Thick Freeport” basin,
fusain was found to be more abundant at Springdale
(3.6 percent). Farther east, seven percent fusain was
recorded in the Armstrong mine. The bulk of the fu-
sain in the latter mine is confined to the uppermost
seven inches of the coal in the form of lenticles and
knife-edge partings mentioned earlier As the fusain
percentage is increased, the anthraxylon fraction is
lowered somewhat.

In creased fusain in the upper pari of the normal
coal is often accompanied by an increase of detrital

TABLE I

PETROGRAPHIC CONSTITUTION OF BEDS
UPPER FREEPORT COAL

UPPER BED

MINE

COUNTY

PERCENT

Anthraxy

Ion Attritus

F usain

Wildwood *

Allegheny

29

67

4

Springdale

Westmoreland

43.6

51.6

4.8

Armstrong

Armstrong

MAIN BED

Wildwood *

Allegheny

57

42

1

Springdale

Westmoreland

57.5

38.9

3.6

Armstrong

Armstrong

52.5

40.5

7.0

* Wildwood data from U. S.

Bureau of Mines T.P.

564.

mineral matter. Over ancient highs, the combination
gives rise to the capping bone layer found in the
normal Upper Freeport coal. In the opinion of the
writer, this layer is the product of local sub-aerial
oxidation which gives rise to the fusain and reduces
the percentage of organic matter relative to the min-
eral matter. Although the bony unit can be detrimental
petrographically determined coal quality is not affect-
ed below the layer. One exception was found during
the investigation. The patch of shaly coal and car-
bonaceous shale found in the southeastern quarter of
the Freeport quadrangle (Figure 3) was undoubtedly
formed upon a local rise that was never covered
sufficiently with peat to produce a good coal.

Ash softening temperatures reported by the U. S.
Bureau of Mines (1939) were plotted upon a map to
ascertain whether or not a correlation exists between

k”

188

the original deposition and the character of the ash
fraction. This map is reproduced as Figure 5. In the
“Thick Freeport” area, no correlation can be esta-
blished. However, a limited degree of correlation is
suggested in the Freeport quadrangle. The ash soft-
ening temperatures along depositional highs are high-
er than those of the intervening depositional lows.
Additional analyses will be needed to determine the
extent of variations of ash fusion temperatures and
the causes for those variations.

FIG. 5 Variation of Upper Freeport coal-ash softening
temperature (°F). Data sources, U. S. Bureau
of Mines and Pennsylvania Geological Survey,
Atlas A-36.

In summary, the Upper Freeport coal was depos-
ited upon a surface whose topography was somewhat
similar to present structure in the study area. High
areas in the depositional floor were detected by chang-
es in number of basal partings and are correlated with:
1) present coal structure, 2) the presence of uppermost
coal layers rich in detrital mineral matter and fusain,
and 3) a tendency for a sandstone roof and attendant
rolls and cutouts. Ash softening temperature may
correlate in normal coal development areas to a limit-
ed extent. The findings listed above suggest that a

close relationship exists between the character of
coal and the geology of the area. A better understand-
ing of these relations might well aid in future explor-
ation and benefication in other coals and other areas
once the responses of individual coals to depositional
features are known.

REFERENCES

Ashley, G. H., J. D. Sisler, J. F. Reese, 1925-28.
Bituminous Coal of Pennsylvania. Pa. Geol. Survey,
4th series, Bull. M-6, pts I, II, and IV.

Hughes, II. Herbert, 1933. Atlas of Pennsylvania, No.
36, Freeport Quadrangle, Pa., Pa. Geol. Survey,

4th series.

Koppe, Edwin F., 1958. Areal distribution of partings
in the Upper Freeport Coal, Freeport Quadrangle,
Pa., Pa. Academy of Science Proc., vol. 32: 128-132.
Rayburn, .]. M., 1924. The deposit of double-thick Upper
Freeport coal situated in the valley of the Allegheny
River in Allegheny, Butler and Westmoreland count-
ies, Pennsylvania. Engr. Soc. Western Pennsylvania
Proc., vol. 20: 27-44.

Richardson, G. B., 1932. Geology and coal, oil, and
gas resources of the New Kensington Quadrangle,
Pennsylvania. U. S. Geol. Survey Bull. 829.
Thiessen, Reinhardt, and G. C. Sprunk, 1935. Micro-
scopic and petrographic studies of certain American
coals. U. S. Bureau of Mines Tech. Paper 564.

U. S. Bureau of Mines, 1939. Analyses of Pennsylvania
bituminous coals. Tech. Paper 590.

ACKNOWLEDGMENTS

The writer would like to express his appreciation
to the many persons and companies who gave generous-
ly of their knowledge and provided access to mines dur-
ing the course ox this study. Particular acknowledg-
ment is given to the personnel of the Allegheny-
Pittsburgh Coal Company, Greensburg, Pennsylvania,
and the Hicks Coal Interests, Leechburg, Pennsylvania,
who furnished samples for the petrographic study.

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